Mentzelia obscura |
Mentzelia strictissima |
|
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Pacific blazing star |
grassland blazingstar |
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Habit | Plants candelabra-form, 8–45 cm. | Plants biennial, candelabra-form. |
Stems | solitary (or multiple as wound response), erect, straight; branches distal, distal longest, antrorse, straight; hairy. |
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Leaves | blade 28–70 × 5.8–17.2 mm, widest intersinus distance 3.4–11.4 mm; proximal oblanceolate, lanceolate, or elliptic, margins dentate to pinnate, teeth or lobes 10–20, perpendicular to leaf axis, 0.9–3.1 mm; distal lanceolate, base usually not clasping, rarely clasping, margins usually dentate, occasionally serrate, teeth 8–18, usually perpendicular to leaf axis, occasionally slightly antrorse, 0.6–5.4 mm; abaxial surface with simple grappling-hook, complex grappling-hook, and needlelike trichomes, adaxial surface with simple grappling-hook and needlelike trichomes. |
|
Basal leaves | persisting; petiole present or absent; blade linear-lanceolate to linear, margins usually irregularly deeply lobed, lobes pointed. |
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Cauline leaves | petiole absent; blade ovate-lanceolate to linear, to 15(–22) cm, margins few-lobed or entire. |
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Bracts | green, ovate to ovate-lanceolate, 2.9–8.2 × 1.1–1.9 mm, width 1/8–1/2 length, not concealing capsule, margins entire. |
margins entire or toothed. |
Flowers | sepals 2–6 mm; petals yellow to orange proximally, yellow distally, 3–8 mm, apex rounded or acute apex; stamens 20–40, 2–7 mm, filaments monomorphic, filiform, unlobed; styles 2–6 mm. |
petals white, 14.7–22(–24.4) × 1.9–4.4 mm, apex acute, glabrous abaxially; stamens white, 5 outermost petaloid, filaments narrowly spatulate, slightly clawed, 13.3–23.1 × 1.3–3.1(–4.4) mm, without anthers, second whorl without anthers; anthers straight after dehiscence, epidermis smooth; styles 7.6–12.9 mm. |
Capsules | clavate, 11–31 × 1.5–3 mm, axillary curved to 250° at maturity, usually inconspicuously longitudinally ribbed. |
cup-shaped to cylindric, 10.2–20.1 × 6.7–9.6 mm, base rounded to occasionally tapering, not longitudinally ridged. |
Seeds | 15–50, in 2+ rows distal to mid fruit, tan, usually not, occasionally sparsely, dark-mottled, usually irregularly polygonal, occasionally triangular prisms proximal to mid fruit, surface colliculate under 10x magnification; recurved flap over hilum absent; seed coat cell outer periclinal wall domed, domes on seed edges less than 1/2 as tall as wide at maturity. |
coat anticlinal cell walls wavy, papillae 3–8 per cell. |
2n | = 36. |
= 20. |
Mentzelia obscura |
Mentzelia strictissima |
|
Phenology | Flowering Feb–May. | Flowering May–Oct. |
Habitat | Sandy to rocky washes or slopes, desert scrub, Joshua-tree woodlands, roadsides. | Arid grasslands. |
Elevation | 200–1700 m. (700–5600 ft.) | 800–1800 m. (2600–5900 ft.) |
Distribution |
AZ; CA; NV; UT; Mexico (Baja California, Sonora)
|
NM; TX |
Discussion | Mentzelia obscura is morphologically intermediate to M. desertorum and M. albicaulis and is known to occur in mixed populations with both species. Reliable discrimination among these species usually requires mature seeds. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
See discussion under 5. Mentzelia nuda. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 540. | FNA vol. 12, p. 505. |
Parent taxa | Loasaceae > Mentzelia > sect. Trachyphytum | Loasaceae > Mentzelia > sect. Bartonia |
Sibling taxa | ||
Synonyms | Nuttallia strictissima | |
Name authority | H. J. Thompson & J. E. Roberts: Phytologia 21: 284. (1971) | (Wooton & Standley) J. Darlington: Ann. Missouri Bot. Gard. 21: 163. (1934) |
Web links |